1. Field of the Invention
This invention relates to methods and apparatus for storing magnetic fields of any configuration in such a way that the field may be varied in a controlled and reproducible manner utilizing superconductors in the persistent current state. This invention also provides for methods and apparatus for creating a complex magnetic field by means of flexible modular superconducting tubes, each containing a stored magnetic field. Furthermore this invention relates to the production of a large volume and/or complex magnetic field by combining small superconducting modules in each of which is stored a small part of the overall field. Finally the method and apparatus disclosed in this invention allow the production of the most miniaturized magnetic field. Means are provided for increasing the fidelity, the magnitude, and the stability of the stored magnetic field.
2. Description of the Prior Art
Since the discovery by Meissner and Ochsenfeld [Naturwiss. 21, 787(1933)] that a magnetic field is expelled from the bulk of a superconductor in the transition from the normal to the superconducting state, this effect (named the Meissner effect) has been considered a crucial property of superconductivity. However it has been found possible to circumvent the Meissner effect.
As shown by Rabinowitz, Garwin, and Frankel [Letters al Nuovo Cimento 7,1 (1973) and Applied Physics Letters 22, 599 (1973)], it is possible to trap and store in hollow or solid superconductors, any configuration magnetic field with high fidelity to the original pattern field. Rabinowitz [IEEE Trans. Magnetics, MAG-11, 548(1975)] has trapped a 17,600 Oersted uniform dipole magnetic field perpendicular to the axis of a Nb.sub.3 Sn hollow cylinder. This is the highest value reported to date. Even higher values are possible. The stored fields may be highly stable.